It is known to use cleaning devices for cleaning water tanks or reservoirs, and particularly swimming pools to clean the bottom and, optionally, the walls of the pool, the apparatus being operated from outside of the pool. It is possible, in principle, to continuously control such a cleaning apparatus so that it consecutively travels across the bottom of the pool in a sequence of paths such that it travels over the complete surface of the pool bottom and accomplishes total cleaning of the surface. It is known also to operate such cleaning apparatus in an automatic manner. For this purpose, one known cleaning device has sensing rods which cause reversal of the direction of travel upon contact with the pool wall or some other obstacle, simultaneously setting a new course of travel. The apparatus then moves on its new course until the next travel direction reversal or change takes place. A disadvantage of this apparatus is that there is no systematic traversing of the pool bottom. The apparatus merely travels backward and forward over the pool bottom and it is quite possible for certain areas to be traversed several times while other areas are not traversed at all.
In another known apparatus for automatic operation, the sensing rod or rods must be set at a predetermined angle as a function of the pool size so that, after covering a particular travel path, the return travel path is inclined with the direction of the first one and then the next travel in sequence is parallel with the first. Quite apart from the fact that the inclined path is not controlled and can, consequently, be influenced by unevennesses or the like, certain areas at the start and end of the travel path are traversed twice. This apparatus must be monitored to ensure complete cleaning of the pool bottom despite the automatic reversal and angular travel.
In another known apparatus, the performance of the individual, automatically performed partial operations during travel direction reversal and direction change are determined by a microprocessor, but the adherence to a course is not ensured in this apparatus and, consequently, the apparatus can be caused to stray from its course by obstacles.